This is probably a dumb question, or at the very least a very beginner question. I've been using python to play/test with LangChain, RAG and running an LLM locally (via HuggingFacePipeline/HuggingFaceHub). I'm curious...

1. How might LlamaIndex relate or fit into this? I mean, is it a competing framework vs. LangChain? I see in the docs it can work with LangChain, so I'm not sure what the purpose of one vs. the other is.
2. If you use LlamaIndex, can it replace LangChain or is it supposed to work with another framework for the rest of the pipeline? Like, LlamaIndex is focused on connecting to our data sources, but then you pass that info to a LangChain pipeline?
3. Since I'm looking to run an LLM locally, Ollama has popped onto my radar. In my mental model, I'm not sure where it fits in. I don't think it's a framework like LlamaIndex/LangChain, but so far I haven't needed it (Ollama), so I'm not sure what "problem" it solves beyond using HuggingFacePipeline/HuggingFaceHub to download and use models locally.

Thanks!